Method and apparatus to provide safety checks for neural stimulation
Electronic neural tissue stimulators for controlling the level of electrical stimulation in order to prevent damage to the neural tissue. Methods presented in the disclosure include detecting current leakage via electrode impedance measurement, electrode capacitance measurement, and testing the electrode response to a test current pulse. Apparatus presented in the disclosure include circuitry and systems capable of performing the methods disclosed.
1. A method of controlling the stimulation of neural tissue comprising:
providing an implantable neural stimulator driving an array of electrodes suitable to stimulate neural tissue;
generating a test current pulse in said implantable neural stimulator applied to an electrode of said array of electrodes during stimulation of tissue;
shorting said electrode to ground;
taking at least one measurement of an IR voltage drop across said electrode during stimulation of tissue;
calculating a maximum voltage prior to shorting said electrode to ground, from at least one IR voltage drop measurement; and
comparing said maximum voltage to a predetermined voltage value.
2. The method according to claim 1 , further comprising
determining if said electrode needs to be shut down based on the step of comparing and
shutting down said electrode if the determining step determines that said electrode needs to be shut down.
3. The method according to claim 1 , further comprising
calculating resistances of said electrode from at least the IR voltage drop measurements and said test current pulse,
wherein said predetermined voltage value is determined using the resistances of said electrode.
4. The method according to claim 1 , wherein the test current pulse are biphasic, comprising an anodic pulse and a cathodic pulse.
5. The method according to claim 4 , wherein the test current pulse are configured such that the duration of the anodic pulse is equal to the duration of the cathodic pulse and equal to the duration between the anodic and cathodic pulses.
6. The method according to claim 5 , further comprising:
providing at least one biphasic stimulating current pulse to stimulate neural tissue,
wherein the test current pulse are of shorter pulse duration and lower maximum current than any biphasic stimulating current pulse.